If radiologists could design the perfect modality for guiding interventional procedures, the resulting technology would undoubtedly produce high-quality images without exposing patients to any ionizing radiation. So given the widespread availability of MRI, why are so many interventions still performed in the angiography suite?

The absence of ionizing radiation is one of the main arguments in favor of interventional MRI. However, even fervent supporters of this technology appreciate the many practical difficulties involved in providing real-time MR image guidance. Despite this, the potential benefits suggest that today's interventional toy could still become the routine tool of tomorrow.

Figure
MRI was used to guide placement of active catheter in aorta of pig (left). Embolization was subsequently performed in upper right renal parenchyma. (Provided by M. Bock)

Speakers at Sunday's special focus session explained exactly why interventional MRI is well worth the effort.

The term "interventional MRI" covers a broad spectrum of procedures, ranging from straightforward biopsies to more complex cardiovascular repairs. To reflect this, the session covered a wide variety of clinical applications, with an emphasis on the future.

Following the increased availability of MR mammography, some imaging clinics now use MRI to guide the biopsy of suspicious lesions in the breast. Providing MR-based breast imaging or even screening without this interventional capacity simply does not make sense, said Prof. Dr. Arno Bücker, who chaired the session.

"If you perform MRI and you see a lesion on the images that was not visible on x-ray mammography, you need a way to localize and biopsy that lesion under MRI guidance," said Bücker, a professor of radiology at Saarland University Hospital in Homburg, Germany.

Interest in MR-guided endovascular interventions is growing, too. MRI has been used to guide puncture in the bile duct and renal system during percutaneous cholangiography with drainage and percutaneous nephrostomy. The modality is then used to control localization of the catheter and guidewire.

MRI can visualize both the vessel wall and surrounding tissue when imaging vessels with atherosclerotic plaque. Animal experiments have shown almost all cardiovascular interventions to be feasible, including the catheterization and stenting of coronary arteries, according to Prof. Dr. Gabrielle Krombach, professor of radiology at Aachen University Hospital in Germany.

Figure
MR-guided intra-arterial injection (Gd-DTPA) through catheter positioned in celiac trunk with subsequent follow-up. In contrast to conventional fluoroscopy, full 3D data sets were acquired. (Provided by M. Bock)